In staff pose we are extending the legs out. We are pointing the toes up so that the feet are flexed, firmly planting the pelvis in the sitting bones into the Earth. We are planting the legs into the Earth, feeling the quadriceps engaged. Planting both palms of the hands firmly upon the Earth. Now imagine that that string is pulling up the crown of our head towards the sky. It seems like a simple pose doesn't it but feel how much work it requires to align the body in this way. Keep the spine nice and straight and imagine that there is something pulling you up right from the center of your head. So we're increasing the space between the vertebra. We are improving the mobility and the alignment of the spine, breathe and breathe and breathe. A lot of work for such a simple pose.